Process of and apparatus for testing belts



March 4, 1930.

c. A. NORMAN PROCESS OF ANDAPPARATUS FOR TESTING BELTS Filed Jan- 1929 2 Sheets-Sheet 1 March 4, 1930.

C. A. NORMAN PROCESS OF AND APPARATUS FOR TESTING BELTS 2 Sheets-Sheet 2 Filed Jan. 21, 1929 gwuento'b clearly passer t FYUN-HTED STATES PATENT Application filed January 21, 1928. Serial R0. 388,935.

-This invention relates to testing power transmitting belts, particularly such as are u'sedfor driving parts of machinery, but it is applicable to all kinds of belts, both large and e small. The invention aims to determine in a shorttime and with a minimum use of power theuseful life of a belt under controlled conditions of operation, as compared with similar belts. 7 7 10 The method and apparatus forming the subject matter of this application are. de-' signed to meet theimportant practical needs comparative belt testin for capacity and endurance when subjecte to the usual ser- A 1 vice conditions in a convenient and satisfactory way. v

The object of my invention is not only to reproduce actual service conditions as nearly as possible, but also to provide for running the belt under test at all usual speeds with a measurable tension difference corresponding to the power transmitted, and with a measurable sh or creep, and to provide for overload- 19 in an for excess speed such as to hasten the 5 fallure of belts being tested to destruction.

Oneway of carrying. out the method consists in the running of two belts in parallel on pulleys of slightly difl'erent diameters, as shown in the accompanying drawing, so that one drive tends to-impart a lower speed to,

the driven shaft than the other. In consequence the first belt acts as a brake on the second and there is established an enforced slip of amount determined by the pulley diameters. In other words, one belt transmits power from the power driven shaft to the second shaft and the other belt returns the same power to the first shaft, minus the drive losses. No power is taken 0d the second shaft, otherwise. 1

The drive tendin to impart the higher speed to the driven s aft has its tight side on the usual pulling side of the drive, the drive tending to impart the lower speed has its ti ht side on the opposite side.

n the accompanying drawings Fig. 1 which shows in perspective a preferred embodiment of one form of belt testing machine carryin .out the invention, illustrates very ow such a device operates when runries a weight support 17 on ning at approximately 1000 R. P. M. under light load, the two slack strands being on opposite sides of the pulleys, and Figs. 2, 3 and 4: are diagrammatic representations of modifiedmachines embodying my invention.-

Referring to Fig. 1 of the drawings, the machine illustrated therein comprises a driving shaft 11 and a driven shaft 12. These shafts are journalled in a supporting frame shown as comprised-of a stationary su port 13 carrying the driving shaft 11, an a relatively movable crosshead 14 carryin the driven shaft 12. This relatively mova le crosshead has connected to it means for pulling it away from the stationary member by a predeter 55 mined force. This means, as shown, comprises a wire rope or the like 15 attached to the movable member 1 1 and passing over a pulley16. The free end of this rope 15 car- Weights '18. In the embodiment shown the crosshead 14 is slidingly supported by guides Mounted on the driving shaft 11 are two pulleys 20 and 21, of slightly diiEere-nt diam- I eters. The driven shalt 12 also fixed thereon pulleys 22 and 23, also unequal in diameter. As shown, pulley 20 is slightly largerthan' pulley 21, pulley 22 is equal in size to pulley 21 and pulley 23 is equal in size to pulley 20. The pulleys are aligned so that two belts 24; and 25 may he placed, respectively, around pulleys 20 and 22 and pulleys 21 and 23. The pulleys being proportioned as above set forth, these baits will he of equal lengths.- The driving 11 may he driven by any suitable means. ii. belt drive 26 passed over a pulley 2'? ried by the 11 constitutes the means shown.

As shown by the arrows drawing, the shafts 11 and 12 .ig clockwise and the belt running pulley 29 to the pulley 22 tends to d iven shaft 12 at a speed greater ill. 1 speed of shaft 11.v The belt'25 r1: pulley 21 to the larg drive the shaft 12 at a shaft 11.

Julley 23 tends to less than that or [as both 22 and 23 are fixed to shaft 12, it folio" belt 2 1, tending to drive the shaft greater speed and mi which are placed l by the ratio of diameters of the pulleys,

which we will call the accelerating belt, is worked against bi belt 25, which we will 0 the decelerating elt. In other words, belt 24 is transmitting power to shaft12, and belt 25 is returning the same power, minus the losses, to shaft 11 outside supply to shaft 11 of only sufiicient power to overcome the losses. clearly shown in the drawin the upper sideof belt 24: and the lower si e of belt 25 run with practically no tension so that all of the tension applied by the welghts 181s divided between the tight sides 0 the two belts. If the pulleys 20 and 21 are of but slrghtly d fferent diameter, the total tension is substantially equally divided between the tight sides of belts 24 and 25. The slip is determmeg an the tension in the belts is produced by dead weights pullin on the s 'ding cross head which carries t e driven shaft. Because one side of each belt is very slack, the tenslon difierence in each belt is nearly equal to half the total tension produced by the dead wei hts.

e machine thus operated consumes only the small amount of power necessary.to cover the belt and bearing losses, and involves no complicated driven machinery, and at the same time reproduces all the essential con: ditions of a real power transmission By varying the slip, the pulley diameters, the speed, and the load, the life of-the belt can be reduced from months and years to less than an hour. Quick indications of the effect of the various factors determining belt life may thereby be obtained.

The principle here described is, of course, not applicable merely toV-belts, but may also be applied to ropes, flat belts, and other types.

As the lineal speeds of the several pulleys are known the slip and/or creep of the two i belts is readily determined, and the pulleys may be so related in size as to result in sired percentage of slip and creep. This slip and creep, in any belting installation, results in heating of the belt. In rubber belts the temperature the belt assumes in running is a matter of supreme importance. Many investigations have been carried out in order to determine what loads, speeds, etc, may be applied to a given belt without raising the belt temperature to a serious amount. The apparatus of this invention is particularly suited for enclosure in a receptacle wherein the temperature can be artificially maintained at any degree desired, so that its effect on belt life can be determined without'any disturbing factors due to variations in load, speed, etc. Thusbelting can be tested for heating effect with regard to the conditions under which it may be used, as well as with regard to the excess of temperature-of the belt over the thus necessitating the "stant lineal speed, are re roduced.

any (lo-- surroundin caused by s p, etc. v

It will be notedthat with the machine di8- temperature due tothe heating closed, a constant tension is maintained on the belts des 1te the stretch of the same as,

shaft 12 is rawn away from shaft 11 to;

compensate for stretch. Thus the conditions /J/ of constant power transmission under con- Obviously machines or carrying out the method of this invention may take other forms than that shown in .Fig. 1, for example, shaft 12 might merely hang in the loops of the belt below shaft 11, and have hanging to it weights corresponding to the total load desired to be applied, thus'doing away with certain supporting members where the speed, load, etc., would permit. If thus arranged, the weight of shaft 12 and 7 its assembled elementshanging in the loops of the belts would have to be added into t' e total tension which-is divided between the tight sides of the two belts when running. Such an arrangement is shown in Fig. 2, wherein the parts corresponding to similar parts in Fig. 1 are indicated bi similar reference numerals modifiedby t e variant letter a. Y

Moreover, as indicated diagrammatically in Figs.,3 and 4, if it is desired to obtain an. absolute and positive value for the sli and tight side tension of one belt, and to det'en mine separately the slip and creep of the belt, one of the belts can be run on two pulleys of e ual diameters, as indicated as 28 or 28 in igs. 3 and 4, so that the slip and creep on each pulley will be the same, and the other belt can be replaced by a positive transmission, such as a chain drive or gear drive between the two shafts to enforce a positive difference in rotative speed of the two pulleys. With such an arrangement, any means such as a universal joint in the movably mounted shaft, or an idler in the gearing, or other equivalent means can be usedto allow all dead weight load to be applied to the belt being tested and to allow movement of the movably mounted shaft, as desired.

Fig. 3 shows diagrammatically an arrangement wherein equal sized pulleys 28 are used, the positive drive being eflected by the sprockets and chain 29, 30 and 31", the universal joint 32 providing for the application to the belt running on pulleys 28 of Obviously the positive drive may be either the accelerating or decelerating drive, as the positive slip and creep will be, enforced 7 whether the belt is transmitting power from the power driven shaft (corresponding to 11) to the second shaft, or returning power flrlorfn the second shaft to the s a t.

. ing may be greatly reduced; a. redetermined slip and creep may be enforce to re roduce certain working conditions and eating eifects; artificial temperature conditions may be maintained throughout the test; and the belt may be tested at full war and all the power transmitted to the elt driven shaft may be returned to the belt driving shaft except what is used up in friction and other drive losses, thus necessitating supplying to the,system only suflicient power toovercome the losses.

The invention is not limited to the specific embodiments of the method and apparatus illustrated herein, but I claim the following:

1. A method of testing belts, including the operation on a single shaft, of two similar belts to be tested, which comprises, operating one of said belts with slip sothat it tends to accelerate the shaft, operating the other of said belts with slip so that it tends to decelerate said shaft, and utilizing the power taken ofi" the shaft by said decelerating belt, augmented by sufiicient power to sup ly the drive losses, to drive the accelerating 1t.

2. A method of testing belts, including the operation of two belts on a set of'interconnect-ed pulleys, which comprises, operating one of said belts with slip so thatit tends to accelerate the set of interconnected pulleys and operating the other of said belts with slip so that it tends to decelerate the set of interconnected pulleys, utilizing the power taken from the set of interconnected pulleys by said decelerating belt to drive the accelerating belt, and adding to the system suficient power to supply the losses therein.

3Qln a method of testing belts including the operation a system of two power transmission means with an interconnecting power transmission means and the utilization of a belt being tested as at least one of these three power transmitting means, the steps of operatingone of said power transmission means so that it to accelerate the interconnecting power transmission means, operating the other of power tranmission means so running the belt on two pulleys,

power drivenv The invention has the followin 'advanr. tages, viz: the time and expense of elt testrunning the belt on two pulle s,

that it tends to decelerate the interconnecting power transmission means, transmitting the power taken from the mterconnectin power transmission means by said dece erating power transmissionmeans to drive the accelerating power transmission means of the system, and adding to the system sufiicient power to supply the losses therein, thereby enforcing slip of the belt beingtested and effecting economy of power in testing.

' 4.'In belt testing, the method including enforcing a difference in peripheral speeds of the two pulleys to maintain a definite percentage of slip and creep, and maintaining a substantiall constant tension on'the tight side of the belt.

5. In belt testing, the method including enforcing s of the, two percentage of maintaining a a difference in peripheral spec pulleys to maintain a definite slip and creep of the belt and substantially constant total tension on the belt;

a 6. In belt testing, the methodwhich in-- cludes mechanically predetermining the tension and slip and creep for the belt to be tested, and operating the belt at any 'speed for any period of time up to the failure period whlle maintaining substantially constant the predetermined factors of the test. 7. The method of belt testing which in} cludes supplying power to and enforcing predetermined slip of a belt to be tested, said supplied power bein composed of returned transmitted power rom the beltand sufficient additional power to overcome the losses in the system.

' 8. The method of belt testing which includes transmitting power through a slipping belt, re-utilizing the major partof the transmitted power in driving the belt, and adding to the system just sufficient power to overcome the losses therein while main taining a substantially constant tension in the tight side of the belt and substantially ping belt, re-utilizing the major part of the transmitted power in driving the belt, and

adding to the system just suficient power to overcome the losses therein while maintaining a substantially constant tension in the tight side of the belt. I

10. That improvement in belt testing which includes transmitting power through a slipping belt, re-utilizing the major part of the transmitted power in driving the belt, and adding to the system just suficient power to overcome the losses therein.

11. In a belt tester; a mechanical systempartly comprised of a pair of interconnected pulleys and a pair of belts each operating on one of said pulleys and of which one slips in the direction of drive and tends-to accelfthe opfiosite direction and tends "to e pulleys and at least one of which from the interconnectedpulle s by said decelerating belt to drive sai I eluding a shaft,a

erate the shaft, a second belt tending to deerate the pulleys while the other sli s' erate t we is a belt under test, said system also includ-' ing means for transmitting the power taken accelerating belt; and means-associated with said system'for adding sufiicient power thereto to supply the losses therein.

12. In a belt tester,a mechanical system infirst belt tending to accelcelerate ,the shaft whereby slippage of said belts is enforced, and means for transmitting the power taken from the shaft by said decelerating belt to drive said accelerating belt, at least one of said belts being a belt under test;and means associated with said system for adding sufiicient'power thereto to supply the losses. therein.

13. A mechanical system including. an in terconnecting power transmission means, two power transmission means operably connecttested; and means associated with said systesting, and means for enforcing a substanthro hout the test.

18. n a machine for testing belts; means on which the belt to be tested is operativel mountedfor transmission of power inclu means for passing power to be transmitmitted power from the belt, and means for enforcing shp of said belt and returning the transmltted ower from said last named means less t e losses in the s stem'to the means for gassing gmer to t e belt; and means for a ding su cicnt power to the system to supply the losses therein.

.tially constant slip and creep of. the belt to the belt, means for taking the trans- 19. A mechanical system for testing belts including through the belt to be tested, and means for enforcing sliplof said belt and returning and re-utilizing t e major part of the transmitted power to drive the belt; and means associated with said system for adding suificient power thereto to supply the losses therein.

means for transmitting power- In testimony whereof, I have signed my name to. this specification.

CARL A. NORMAN.

tem for adding suiiicient power thereto to supply the losses therein.

14. In a machine for testing belts, rotatable pulleys on which is mounted the belt to be tested, means for-enforcing a difference in peripheral speeds of the pulleys during rotation to maintain a definite percentage of slip and creep of the belt, and means for maintaining ,a substantially constant tension on the tight side of the belt.

15. In a machine for testing belts, rotatable pulleys on which is mounted the belt to be tested, means for enforcing a difference in peripheral speeds of the pulleys during rotation to maintain a definite percentage of slip and creep of the belt and means for maintaining a substantially constant total tension on the belt. a

16. In a machine for testing belts, means on which the belt is operatively mounted for testing, means for enforcing a substantially constant slip and creep of the belt throughout the test, and means for maintaining a. substantially constant tension on the belt throughout the test.

17. In a machine for testing-belts, means on which the belt is operatively mounted for- 

